U.S. Pat. No. 5,733,914 (which is incorporated herein by reference) describes a series of pyrido[2,3-d]pyrimidines that inhibit protein tyrosine kinase mediated cellular proliferation. The compounds are anti-angiogenic agents, and as such are useful for treating cancer, particularly leukemia and breast cancer. The U.S. Pat. No. 5,733,914 patent teaches that a particularly preferred group of compounds are substituted at the 2-position with an arylamino group, and that the aryl moiety can be a pyridyl group. 2-(4-Pyridyl)amino-pyrido[2,3-d]pyrimidines appear to be a preferred group of compounds because of their metabolic stability and tyrosine kinase selectivity. One such compound, namely 2-(pyridin-4-ylamino)-6-(3,5-dimethoxyphenyl)-8-ethyl-8H-pyrido[2,3-d]pyrimidin-7-one, is currently being studied as a possible clinical candidate for treating cancer.
Because these compounds are commercially viable anticancer agents, the need exists for a synthetic process that affords the desired compound in high purity and satisfactory yields. This invention provides a commercially viable process for making such pyridylamino-pyrido[2,3-d]pyrimidines.